The objective of this project is to show whether neutron therapy (using TAMVEC cyclotron) can improve the control rates or decrease the incidence of radiation sequelae. Pretherapeutic studies have been undertaken in the following areas: 1) Physics and nuclear engineering - to design collimation, determine isodose distributions, dose measurements, LET spectra measurements, neutron energy spectra, eta/gamma ratios, and whole body dose measurements; 2) Cellular radiobiology - to determine RBE and OER for various neutron energies, fraction sizes and depths; 3) Small animal tissue radiobiology - to determine the RBE for intestinal mucosal damage and other normal tissue changes; 4) Large animal tissue radiobiology - to determine the RBE of pig skin for the neuton energies to be employed; 5) Oral cavity radiobiology - to evaluate effects of induced radioactivity, mucosal reactions, and methods of diminishing these reactions; and 6) Animal tumor therapy - to provide information on normal tissue damage, treatment planning, and tumor control. The clinical trial in human tumors has been instituted, utilizing patients with bulky head and neck, breast lesions, and metastatic disease of selected sites and histologies.